Televisions, computer monitors and other display devices exist in a great multitude of display sizes and aspect ratios. For example, conventional television displays have a 4:3 (1.33:1) aspect ratio (hereafter referred to as a standard display) while widescreen displays, such as theater or HDTV displays, have a 16:9 (1.78:1) aspect ratio. There are also still wider displays having aspect ratios of 2.39:1 or 2.35:1. Moreover, a given display unit should be able to display the great multitude of video signal formats that exist. In order for a given display unit to display a format other than its own native format, various techniques are used to shrink or extend the aspect ratio of the normative format. Many of these techniques involve projecting the normative image in its original format onto the native display and simply blackening the “gaps” where no image information exists.
Letterboxing is the practice of transferring wider video formats, such as 16:9, to more square formats while preserving the original aspect ratio. The resulting video display must include masked-off areas above and below the picture area, often referred to as black bars, or, more accurately, as mattes. In contrast, pillarboxing, or windowboxing, is necessitated when video that was not originally designed for widescreen is shown on a widescreen display. The original material is shrunk and placed in the middle of the widescreen frame while vertical black bars are placed on either side. Lastly, there are sometimes instances in which standard ratio images are presented in the central portion of a letterboxed picture, resulting in a black border all around. This effect is referred to as matchboxing, and obviously wastes a great deal of screen space as well as reduces the resolution of the original image.
Although a controller for a television display generally “knows” that the incoming signal it is receiving is a video signal, the controller generally does not know the format of the incoming signal it is receiving. In the case of computer monitors, or monitors in general, even less is known about the incoming signal; that is, the monitor does not know whether it is receiving a video signal (such as from a DVD), a textual signal (such as from a computer), or a combination of both. Hence, it is difficult for the display controller to know how to best process the incoming signal.
In order to apply image improvement effects, such as color enhancement or other processing to a graphics or video image, it is necessary to know the nature of the image content; that is, it is desirable to know whether the image is largely real (a film or digital recording) or synthetic (artificial or textual image). In the case where a given display is letterboxed, pillarboxed, or both, it is further desirable to know which portions of the image frame are real and which are synthetic such that appropriate and efficient image processing is accomplished.
Therefore, it would be desirable to automatically determine the image content of an incoming signal into a display unit.